Why do adults continue to play throughout their lives while most other mature mammals cease such behavior? According to researchers at Penn State, playfulness may serve an evolutionary role in human mating preferences by signaling positive qualities to potential long-term mates. "Humans and other animals exhibit a variety of signals as to their value as mates," said Garry Chick, professor and head of the Department of Recreation, Park and Tourism Management. "Just as birds display bright plumage or coloration, men may attract women by showing off expensive cars or clothing. In the same vein, playfulness in a male may signal to females that he is nonaggressive and less likely to harm them or their offspring. A woman's playfulness, on the other hand, may signal her youth and fertility."